Reclaiming the marshland

Plan: Scientists and engineers are hoping to halt erosion and restore 8,000 acres of mud and grasses at Blackwater Refuge.

September 24, 2002|By Chris Guy | Chris Guy,SUN STAFF

BLACKWATER NATIONAL WILDLIFE REFUGE - In aerial photographs, the encroaching water looks like a black hole in the middle of this 24,000-acre Dorchester County sanctuary, a brackish inland sea that has been gobbling up 150 acres of marshland every year for nearly half a century.

Now, while Blackwater remains the largest stretch of unbroken marsh on the Chesapeake Bay, government scientists and engineers are hitching their hopes for halting losses and restoring 8,000 acres of mud and grasses to a clanking 40-foot dredge boat. For the last month, it has been spewing a stream of sand and mud along a carefully laid-out grid.

"People can stand and look at this huge area of water and think it's wonderful," says Glen Carowan, refuge manager. "What they don't realize is that we're talking about 12 square miles of marsh and vegetation that has been lost since 1940. When we say lost, we mean it's just not there any more. It's gone, replaced by open water."

Carowan and a team from the Army Corps of Engineers, the U.S. Fish and Wildlife Service and Maryland's Department of Natural Resources are nearing the end of a pilot project that might offer the best chance for rebuilding vast marshy tracts that are being eaten away from within.

After studying Blackwater for nearly two years, scientists began what they call "thin layer" dredging last month, taking sand and silt that has built up in channels and ponds throughout the refuge and layering it - from 2 feet to just a few inches deep - over 20 acres along the edges of existing marsh.

"This is really the epicenter of marsh lost in the bay," says Steven Kopecky, the Corps' project manager. "This area still accounts for about one-third of the tidal wetlands in the state."

Restoration, says Corps ecologist Steve Pugh, is important for tens of thousands of migratory waterfowl, as well as other animals - including the endangered Delmarva fox squirrel, 250 species of birds and the largest concentration of bald eagles in the eastern United States north of Florida.

Halting erosion at Blackwater would also boost Fishing Bay, the largest nursery for larvae blue crabs in the Chesapeake, and improve water quality in nearby Tangier Sound, he said.

The test areas at the refuge, corralled by hay bales to prevent newly deposited sand and mud from drifting away until marsh grasses take root, account for less than 1 percent of the marshland that has been lost.

The dredge boat, according to Troy M. Deal, the Florida-based contractor handling the project, "sips sand and mud just like a straw," then sprays it in designated areas. The rig is ideal in Blackwater, where some shallow areas are accessible only in air boats like those used in the Everglades, because it can dredge its way to a site.

The $1 million pilot project goes hand in hand with a four-year, $1.75 million program to eradicate nutria. The South American rodents have exacerbated damage from rising seawater, a problem for low-lying areas throughout the region since their introduction in Maryland in the 1930s.

Unlike muskrats, their smaller native cousins that graze on the tops of marsh grasses, nutria eat the roots of plants, creating deep channels and exposing marsh sediments to tidal and wave erosion. The animals, which number 30,000 to 50,000 in Blackwater, are the targets of a 12-member team that has been trapping and killing them since spring.

"The nutria aren't the only problem, but they increase everything that's happening to the marsh," says Carowan.

With the dredge operation due for completion by the middle of next month, project leaders are uncertain of their next step. No one has begun to put a price tag on what would certainly be a mammoth undertaking, perhaps even dwarfing the $340 million restoration Poplar Island in the Chesapeake Bay just off Talbot County.

"It isn't an issue of whether we can restore a marsh," says Kopecky. "Now it becomes a question of logistics and how cost effective it might be. What sets Blackwater apart is the scale. We're talking about marsh restoration on a massive scale."

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